Air jet spinning machines equipped with the corresponding spinning units are known from the state of the art and serve to manufacture yarn from an elongated fiber strand. In this process, the outer fibers of the fiber strand are wound around the inner core fibers with the help of a swirled air current generated by the air nozzles inside the vortex chamber in the area of a fiber inlet of the yarn forming element and finally form the wrap fibers crucial for desired yarn strength. As a result of that, a yarn with a real yarn twist is formed that is finally led out of the vortex chamber via a draw-off channel and can be wound up around a tube, for example.
Generally, within the meaning of the invention, the term yarn is understood to be a fiber strand in which at least some of the fibers are wound around an inner core. Thus, the term encompasses a yarn in the conventional meaning that can be processed into a fabric, for example, with the help of a weaving machine. However, the invention also refers to air jet spinning machines used to manufacture so-called rove (another name: sliver). This kind of yarn is characterized by being capable of drafting in spite of having certain strength sufficient for transporting the yarn to a subsequent textile machine. Thus, the rove can be drafted with the help of a drafting mechanism (e.g. the drafting system, a textile machine that processes the rove such as a ring spinning machine) before it is finally spun.
In the manufacturing of synthetic fibers such as polyester or a combination of natural and synthetic fibers, deposits are formed on the surface of the yarn forming element. The manufacturing of synthetic fibers encompasses a so-called preparation of the continuous filaments during the manufacturing process. The preparation consists of applying a preparation agent (generally oils with various additives) to allow treatment that can involve drafting the continuous filaments under high rates. These preparation agents continue to adhere partially on the synthetic fibers even in further processing and cause impurities in the air jet spinning machine. The fibers fed to the air jet spinning machine in the form of a fiber strand are generally supplied by a pair of delivery rollers of the spinning nozzle. The pair of delivery rollers can correspond to a front roller pair of a drafting system, which is used to improve the fiber strand presented before it enters the spinning nozzle.
As a rule, a fiber guiding element is arranged in the inlet area of the spinning nozzle through which the fiber strand is guided into the spinning nozzle and finally into the area of the yarn forming element. Spindles having an inner draw-off channel are used most of the time as yarn forming elements. Compressed air is introduced in such a way on the top of the yarn forming element through the housing wall of the spinning nozzle that the above-mentioned rotating swirled air current is generated. This causes the individual outer fibers coming out of the fiber guiding element to be separated and turned over above the tip of the yarn forming element. Later, these detached fibers rotate on the surface of the yarn forming element. Subsequently, the forward movement of the inner core fibers of the fiber strand makes the rotating fibers wind around the core fibers, thus forming the yarn. However, the movement of the individual fibers over the surface of the yarn forming element also causes deposits to form on the yarn forming element owing to adhesions on the fibers from the manufacturing process. Deposits on the yarn forming element can also be caused by damaged fibers. For the same reasons, deposits can also form on the surface of the spinning nozzle's interior. These adhesions are detrimental to the surface finish of the yarn forming element and lower the quality of the manufactured yarn. Therefore, regular cleaning of the affected surfaces becomes necessary to maintain the same quality of the spun yarn.
The surfaces of the yarn forming element can be cleaned manually by periodically disassembling the yarn forming element, but this involves significant maintenance work coupled with the corresponding operational downtime.
On the other hand, EP 2 450 478 describes an equipment capable of cleaning the machine automatically without shutting down the machine. To accomplish this, an additive is added to the compressed air used inside the spinning nozzle for producing the swirled air current. The additive is guided through the compressed air towards the yarn forming element, where it cleans its surface.
Another embodiment to clean the yarn forming element is described in JP-2008-095-208. Here, an additive is likewise fed to the compressed air used for swirling in the spinning nozzle that guides it to the spinning nozzle and thus to the yarn forming element. In the disclosed embodiment, the dosage and addition of the additive is intended to be separate for each spinning unit.
The disadvantage of these disclosed cleaning systems is that the additive dosage depends on the supply of compressed air to the air nozzles. Thus, a dosage independent of this is not possible.
In principle, the same problem occurs when an additive should be added to the fiber strand in order to improve the properties of the yarn manufactured in this way, for example with regard to its hairiness or strength, since in this case the dosage can be regulated in an especially precise way to prevent that too much or too little of the prescribed quantity of additive is applied on the individual fiber strand sections.